Field of the Invention
The present invention relates to an image processing apparatus which performs image restoration.
Description of the Related Art
For an object shot via an image pickup optical system, light emitted from one point cannot be converged to another point and has a minute spread due to an influence of a diffraction, an aberration, or the like that occurs in the image pickup optical system. Such a minutely-spread distribution is referred to as a point spread function (PSF). Due to the influence of the image pickup optical system, the shot image is formed with the PSF convoluted with the image, and accordingly, the image is blurred and its resolution is deteriorated.
Recently, the shot image is typically stored as electronic data, and image restoration has been proposed which corrects an image deterioration caused by an optical system by performing image processing. For example the image restoration using the Wiener filter is known. The image deterioration caused by a shake (image blur caused by a hand shake) can occur at the time of shooting an image. Even when an image pickup apparatus including an image stabilizer is used, image stabilization (image blur correction) cannot be effectively achieved in some cases if an amount of the shake is increased.
Japanese Patent Laid-open No. 2004-239962 discloses an image pickup apparatus which switches restoration processing according to whether or not an image blur correction optical system is driven. Japanese Patent Laid-open No. 2005-252760 discloses an image pickup apparatus which performs restoration processing considering an error of a control position at which an image blur correction optical system is driven.
However, a blurred image (shot image) contains a plurality of points where an optical transfer function (OTF) becomes zero, and thus it is difficult to perform the image restoration. In addition, an image deterioration due to blurring caused by the image pickup apparatus, as well as the image blur (caused by the shake), occurs in the shot image. Difficulty of the image restoration changes depending on characteristics of the image blur (shake) and the blurring. The difficulty of the image restoration means ease of occurrence of a negative effect which is not acceptable in the image restoration. The difficulty of the image restoration is high when the negative effect easily occurs, and on the contrary, the difficulty is low when it does not easily occurs. Japanese Patent Laid-open Nos. 2004-239962 and 2005-252760 do not disclose the negative effect.